This invention relates to equipment that can be used in the drilling and completion of wellbores in an underground formation and in the production of fluids from such wells.
Fluids such as oil, natural gas and water are obtained from a subterranean geologic formation (a xe2x80x9creservoirxe2x80x9d) by drilling a well that penetrates the fluid-bearing formation. Once the well has been drilled to a certain depth the borehole wall must be supported to prevent collapse. Conventional well drilling methods involve the installation of a casing string and cementing between the casing and the borehole to provide support for the borehole structure. After cementing a casing string in place, the drilling to greater depths can commence. After each subsequent casing string is installed, the next drill bit must pass through the inner diameter of the casing. In this manner each change in casing requires a reduction in the borehole diameter. This repeated reduction in the borehole diameter creates a need for very large initial borehole diameters to permit a reasonable pipe diameter at the depth where the wellbore penetrates the producing formation. The need for larger boreholes and multiple casing strings results in more time, material and expense being used than if a uniform size borehole could be drilled from the surface to the producing formation.
Various methods have been developed to stabilize or complete uncased boreholes. U.S. Pat. No. 5,348,095 to Worrall et al. discloses a method involving the radial expansion of a casing string to a configuration with a larger diameter. Very large forces are needed to impart the radial deformation desired in this method. In an effort to decrease the forces needed to expand the casing string, methods that involve expanding a liner that has longitudinal slots cut into it have been proposed (U.S. Pat. Nos. 5,366,012 and 5,667,011). These methods involve the radial deformation of the slotted liner into a configuration with an increased diameter by running an expansion mandrel through the slotted liner. These methods still require significant amounts of force to be applied throughout the entire length of the slotted liner.
A problem sometimes encountered while drilling a well is the loss of drilling fluids into subterranean zones. The loss of drilling fluids usually leads to increased expenses but can result in a borehole collapse and a costly xe2x80x9cfishingxe2x80x9d job to recover the drill string or other tools that were in the well. Various additives are commonly used within the drilling fluids to help seal off loss circulation zones, such as cottonseed hulls or synthetic fibers.
Once a well is put in production an influx of sand from the producing formation can lead to undesired fill within the wellbore and can damage valves and other production related equipment. Many methods have been attempted for sand control.
The present invention is directed to overcoming, or at least reducing the effects of one or more of the problems set forth above, and can be useful in other applications as well.
According to the present invention, a technique is provided for use of an expandable bistable device in a borehole. The bistable device is stable in a first contracted configuration and a second expanded configuration. An exemplary device is generally tubular, having a larger diameter in the expanded configuration than in the contracted configuration. The technique also may utilize a conveyance mechanism able to transport the bistable device to a location in a subterranean borehole. Furthermore, the bistable device can be constructed in various configurations for a variety of applications.